Cut Calories with Low-GI Foods

You've eaten your weight in grapefruit, counted your share of fat grams, and sworn off bread, pasta, and every other carbohydrate, all in an effort to squeeze into your skinny jeans. Now you can finally breathe easier: The next big thing in weight loss isn't low-fat, low-flavor, or low-carb. It's the low-glycemic index diet, and if you haven't already heard of it, you will. Research is beginning to confirm what popular diet plans like The South Beach Diet (St. Martin's Griffin, 2005) have been preaching for years: Eating a diet composed mostly of foods with a low glycemic index may help you cut calories without cravings by balancing blood-sugar levels.

"Good" vs. "Bad" Carbohydrates

In the simplest of terms, a low-glycemic diet is generally high in good carbohydrates (like vegetables and whole grains) and low in bad ones (like chocolate chip cookies). Lean proteins and healthy fats round out the rest. "It's the middle ground between diets that are packed with protein, which promise satiety, and those loaded with fiber, which are the most nutritious," explains Walter Willett, MD, chairman of the department of nutrition at the Harvard School of Public Health. But that's not the whole story. Glycemic-index diet plans are some of the most complicated ever to hit the bookstore shelves. Some allow carrots, some don't. Some say bananas are okay, others say they're not. What most experts do agree on, however, is that following one may not do any harm and can even confer health benefits beyond basic weight loss. Before you try one, here's what you need to know.

The Glycemic Index Equation

The glycemic index (GI) is a system of ranking carbohydrates based on how much they raise blood-glucose levels. It was originally developed for diabetics, but its usefulness has grown with our understanding of the impact blood-sugar levels have on hunger. According to Christine Pelkman, PhD, an assistant professor of nutrition at SUNY Buffalo, the theory goes: You eat a carbohydrate. The rise in blood sugar triggers a boost in insulin production. Insulin reduces your blood sugar, which leaves you feeling irritable and lethargic. You're left at Krispy Kreme's door, begging for a doughnut. "Falling blood-sugar levels can cause you to get hungrier faster," says Pelkman.

Balance Your Blood Sugar Levels

There are lots of things you can do to keep your blood-sugar levels balanced. Daily exercise helps, and so do regularly spaced snacks and meals, but your food choices are key. That's where low-GI foods come in. Foods with a GI lower than 55 raise blood sugar slightly, while those in the 55 to 70 range raise it a little higher; carbohydrates with a GI of more than 70 send it soaring. Low-GI foods have a more moderate effect on blood-sugar levels, primarily because they slow digestion — that's why some low-GI plans call themselves "slow carb."

A number of studies show that a low-GI meal can be more satisfying than a high-GI meal and can help control overeating; some experts speculate that this effect may lead to weight loss. Research also shows that eating a low-GI diet may help prevent insulin resistance, which is a likely culprit in the development of diabetes. "Furthermore, since insulin resistance leads to excess weight gain around the waist, a known risk factor for cardiovascular disease, a diet based on low-GI foods may also be protective of your heart," says David Katz, MD, director of the Yale Prevention Research Center.

Make a Low-GI Diet Work for You

Rigidly following a low-glycemic index diet plan isn't easy. For one thing, it's difficult to know what to eat unless you carry an extensive list like ours around with you. Just try picking out a breakfast cereal: All-Bran has a low GI (38) while Bran Flakes has a high one (74). And, oddly, sugar has a lower GI (61) than whole wheat bread or potatoes. "You can't throw out all of your nutrition know-how because of the index," says Thomas Wolever, MD, PhD, a GI researcher and professor of nutrition at the University of Toronto. "Chocolate cake may have a lower GI than wheat bread, but this doesn't mean it's better for you. You have to take into account that the cake also has more fat, sugar, and calories and less fiber."

Complicating things even further is that GI rankings compare foods based on a set amount of carbohydrates (usually 50 grams), which doesn't always correlate to normal portion sizes. And when you start combining foods, their effect on your blood-sugar levels changes. But before you give in to your doughnut desires, relax. Here's how to reap the benefits of a low-GI diet.

Replace as many as possible high-GI foods in your diet with healthy lower-GI alternatives.

Add or substitute at least one healthy low-GI food at each meal. Include protein and fat whenever you eat a high-GI food.

Choose low-GI whole grains over refined as often as possible.

Reduce the blood-sugar impact of any food by pairing it with one that has a lower glycemic index. For example, smother waffles (high-GI) with blueberries (low-GI).

Slow-Meal Makeovers

Instead of: Instant oatmealTry: Old-fashioned oatmeal

Why: The chewiness of old-fashioned oatmeal is largely due to the high percentage of hard, compact starch granules, as well as fiber. These granules are more complicated to break down, and they slow the digestive process. In contrast, much of the starch in instant oatmeal has been presoftened during processing, so it's digested more quickly.

Why: Stone-ground whole wheat is coarser, which makes it slightly more difficult to digest (that's a good thing). The avocado provides fat and the tomato soup is acidic. Fat and acid both slow digestion by delaying the rate at which food leaves your stomach.

Instead of: PretzelsTry: Apple slices with peanut butter

Why: The apples provide fiber and the peanut butter adds fat, both of which slow digestion.

Why: Like instant oatmeal, instant white rice gets digested very quickly because processing has softened much of the starch granules. Basmati rice is a better choice because the starch granules are more compact. The protein from the chicken or tofu helps slow digestion.